Friction is a force that slows the motion between two objects in contact. Derek wants to determine how the surfaces of objects affect the amount of friction. Which of the following will help test this? Slide a wooden block across a table and then across a rug. Compare and contrast the results. Slide a wooden block across a table; slide a metal block across a rug. Compare and contrast the results.

Slide a wooden block across a table; repeat the action at a faster speed. Compare and contrast the results.

Slide a wooden block across a table; repeat the action by turning the block on its side. Compare and contrast the results.

it can be observed without changing the identity of the object.

it depends on what substance you're talking about as well as many other factors. in quantum mechanics, the observation of particles affects the observers ability to measure certain properties. for example: you can know the velocity of a particle, but you can't know it's position; or you can know it's position, but not it's velocity. it's like trying to find out where a grain of sand is by throwing other grains of sand at it. once you find out where it is, it's been moved. it's also like trying to find an answer to the question of whether or not a tree falling in a forest makes a sound if nobody is there to hear it. paradoxically, the only way to find out is to be there and hear it.

i think is conclusions.i think so